1. Field of the Invention
This invention relates to a valve and more particularly to a rotary valve having a bent valve stem sealed by a bellows which is rotatably connected to an actuator to permit transmission of torque from the actuator to the valve stem through a pressure boundary formed by the bellows without applying torque to the bellows.
2. Description of the Prior Art
In rotary valves, such as butterfly, ball, plug, and the like, for the conveyance of fluids and particularly contaminated fluids at high pressure, as well as, at substantially reduced pressure or under vacuum conditions, it is preferred to utilize static seals as opposed to packed or dynamic seals. Packed and dynamic seals are subject to wear and result in valve leakage, particularly at the pressure boundary between the valve stem and the valve member. A commonly used static seal is a bellows surrounding the valve stem. U.S. Pat. Nos. 1,644,825; 2,659,569; 2,659,570; and 3,811,651 disclose valves that utilize a bellows for sealing around the valve stem between the valve actuator and the valve member.
Conventionally, a bellows when used to seal a valve stem is bonded or welded to the structure of the valve body that supports the rotatable valve member at one end and at the opposite end to a retainer or cap that connects the valve stem to the valve actuator. Because the connections at the ends of the bellows are metal-to-metal, a static seal is formed. It is well known that static seals are not satisfactory for transmitting rotation. Therefore, a bellows, used heretobefore as a static seal is not adaptable for transmission of torque from the valve actuator to the valve stem. It is also known to laterally deflect the valve stem or utilize a crank-like valve stem and hermetically seal the stem. In this manner, the valve stem connects the actuator to the valve member to prevent torsional loading of the bellows, as illustrated in U.S. Pat. Nos. 1,644,824 and 3,811,651.
While it has been suggested by the prior art devices to utilize a bellows as a static seal, particularly in valve applications where contaminated fluids are to be contained, the prior art devices do not permit the transmission of torque through the pressure boundary provided by the bellows. Therefore, there is a need in non-rising rotary valves for a valve stem sealed by a bellows that is supported at its end portions in a manner to permit transmission of torque through the bellows seal without applying torque to the bellows.